Infinitely variable cone pulley transmission

ABSTRACT

In an infinitely variable cone pulley transmission the cone pulley pair on one of the two shafts (driving or driven) is pressed together by a helical coil spring and on the other shaft by a hydraulic force. On the hydraulically operated side the axially displaceable cone disc and the transmission shaft form together a cylinder and piston arrangement. A particularly compact dimensioning of the transmission and the control device is achieved by arranging the pressure pump housing immediately adjacent the transmission housing. The pressure pump housing contains in one block a slide valve for regulating the hydraulic pressure, lines for guiding the pressure liquid, first mechanical elements for automatically sensing and controlling the transmission ratio, and second mechanical means for manually overriding the automatically adjusted ratio.

United States Patent [151 3,704,634

Schrodt 51 Dec. 5, 1972 [s41 INFINITELY VARIABLE CONE 3,618,413 11/1971Cherpes .rmzmn F PULLEY TRANSMISSION [72] inventor: Rudolf Schrodt,Kronberg, Germany [73] Assignee: Relmers Getriebe A.G., Zug, Switzerland[22] Filed: April 21, 197i [2]] Appl. No.: 135,988

[30] Foreign Application Priority Data April 24, i970 Germany ..P 20 I9848.5

[52] US. Cl ..74/230.l7 F [5 l Int. Cl ..Fl6h 55/52 [58] Field of Search..74/230.l7 F, 230.17 A

[56] References Cited UNITED STATES PATENTS 3.280.649 iii/1968 Bruet..74/230.l7 F 3,600,960 8/l97l Karig 74/2301? F 3,600,96l 8/l97lRattunde ..74/230.l7 F

Primary Examiner-C. J. Jusar Attorney-Jennings Bailey, Jr.

l 5 7] ABSTRACT in an infinitely variable cone pulley transmission thecone pulley pair on one of the two shafts (driving or driven) is pressedtogether by a helical coil spring and on the other shaft by a hydraulicforce. On the hydraulically operated side the axially displaceable conedisc and the transmission shaft form together a cylinder and pistonarrangement. A particularly compact dimensioning of the transmission andthe control device is achieved by arranging the pressure pump housingimmediately adjacent the transmission housing. The pressure pump housingcontains in one block a slide valve for regulating the hydraulicpressure, lines for guiding the pressure liquid, first mechanicalelements for automatically sensing and controlling the transmissionratio, and second mechanical means for manually overriding theautomatically adjusted ratio.

PATENTE D 5 8,704,634

SHEET 3 nr 4 INVENTOR RUDD LF SQ HRC DT- f w a r? INFINITELY VARIABLECONE PULLEY TRANSMISSION BACKGROUND OF THE INVENTION The inventionrelates to an infinitely variable cone pulley transmission whichcomprises one pair of cone pulleys on the driving shaft and one pair ofcone pulleys on the driven shaft and an endless transmitting memberrotating therebetween. At least one cone disc in each pair of pulleys isdisplaceable on the shaft in axial direction of clamping thetransmitting member between them and the pressure exerted on the conepulley pairs in axial direction for clamping the transmitting memberbetween them is generated on one side, i.e., either on the driving sideor on the driven side, by hydraulic means and on the other side bymechanical means. On the hydraulically operated side the shaft and aportion of the axially displaceableco'ne disc form together acylinder/piston arrangement to which the hydraulic liquid is transportedby a pump through a control valve. The control valve is adjustable bothautomatically for maintaining or for changing the pre-establishedtransmission ratio and manually for overriding the established ratio.

Infinitely variable cone pulley transmissions of the above type arealready disclosed in the German Pat. No. l 081 733. The pressure inaxial direction on the pulley pair on one side is in the knowntransmissions generated mechanically in dependence on the torque and onthe transmission ratio by cam sleeves having a rising cam gradient. Onepart of the sleeves is stationary on the shaft and the other isconnected to the movable cone disc, and roller members are insertedbetween the cams.

Further, there are infinitely variable cone pulley transmissionsdisclosed in the German laid-open Pat. application No. l 264 196 whichcomprises means for generating the axial pressure exerted on the conepulley pairs on the driving and on the driven side hydraulically independence on the torque and on the transmission ratio. The hydraulicliquid on both sides is supplied to the cylinder/piston aggregatethrough a control valve having a square valve stem. The valve stem isadjustable both automatically by the displaceable cone disc and alsomanually. Further, there is a reducing valve required in the feed-backline from the control valve to the pump for reducing the pressuregenerated by the pump and the control valve on the driving side of thehydraulic unit.

For controlling an infinitely variable cone pulley transmissionhydraulically there are required, besides the cylinder/piston aggregate,at least one pump complete with drive means, a control device includinga safety valve, a reducing valve, a piston valve, means for adjustingthe transmission to a nominal transmission ratio, sensing means forsensing the actual transmission ratio, and means for introducing thehydraulic liquid into the revolving shaft of the transmission side to becontrolled. In the prior-art-transmissions all these elements areassembled in at least three different groups. For this reason an extranumber of complicated parts are required for proper operation. All theseelements and parts are complicated in design and expensive inmanufacture. Besides, a noticeable amount of space is needed for thesegroups. But with the known transmissions these disadvantages are not ofgreat significance because those transmissions are high-dutytransmissions which, for utmost utilization of the material, mustoperate very exactly and with as little a safety margin as possible.

However, for uses where only little or average duty is demanded, aninexpensive and easily maintained yet reliably operating cone pulleytransmission is required. Such uses are, for example, farming machinerylike tractors, harvesting machines etc. for which the known mechanicallyoperated control devices with hand wheel and set spindle are notsuitable because of the great force needed for setting and because ofthe time-consuming and complicated setting procedure. Much better forsuch uses are hydraulically operating control devices which need only asmall force for moving the control elements. But the known hydraulicallycontrolled transmissions cannot be used because, as pointed out above,they are too unwieldly and too expensive to be applied with a low-duty,inexpensive transmission.

It is, therefore, an object of the present invention to provide a simpleand uncomplicated infinitely variable cone pulley transmission with ahydraulical control device without making the transmission complicatedand expensive, so that the latter will be suitable for application witha number of machines which require only an average-duty but reliabletransmission.

SUMMARY OF THE INVENTION The above stated object is attained bygenerating the pressure on the cone discs in axial direction on one sideof the transmission by a helical coil spring and on the other side byhydraulic control means. 0n the hydraulically controlled sidesimplifications are achieved by mounting the pump shaft coaxially withthe transmission shaft and connecting both for joint rotation, and byarranging the pump housing immediately adjacent the transmission housingwith both housings being connected to form one block. The pump housingis at the same time the housing of the control valve. A further housing,again mounted immediately adjacent the transmission housing and the pumphousing, contains a feeler member which extends in axial directionthrough the hollow pump shaft, and which with one end in engagement withthe axially displaceable cone disc and with the other end is with thecontrol valve. An additional lever is provided in the housing formanually ad justing the control valve. The lines of the hydraulic liquidare formed by holes and recesses in the transmission shaft, in the pumpshaft, in the transmission housing, in the pump housing, and also in thefurther housing. The pump shaft extends into the same bore in thetransmission shaft which also conducts the hydraulic liquid.

In the control device according to the invention all elements which arenecessary for hydraulically controlling one side of the transmission areincorporated in one unit which needs only little space and comprisesonly a minimum of single parts. The unit to a great extent makes use ofthe elements and the space thereof which have to be present in any case.Besides, the problem of conducting the hydraulic liquid through therevolving shaft into the cylinder/piston aggregate has been solved in asimple manner. The pump shaft and the transmission shaft rotate at anequal number of revolutions per minute so that the problem ofintroducing the hydraulic liquid from a stationary element into arotating element has been avoided, thus also avoiding any relativemovement at the seal between these two elements. Further. there are noadditional elements required for driving the pump shaft, such as gears,chains, belts etc.

A further advantage of the invention is that the feeler member and thelevers for sensing and adjusting the preselected transmission ratio areshort and practically free from elasticity. The cooperation between theaxially displaceable cone disc, the feeler member and the control valveis therefore very exact and without tiine delay. Besides, since most ofthe lines of the hydraulic liquid are formed by the gear elementsthemselves all movable parts are arranged in the flow of the liquid sothat no dry friction can occur.

It has proven advantageous to install a throttle valve in the returnline next to the control valve and also a pressure relief valve forincreased safety. In a further embodiment of the invention the pressurerelief valve or safety valve is a control valve which, at the same time,performs the function of the safety valve. Thereby a furthercentralization of the mechanical elements, simplification of the designand saving of space is achieved.

The lever for manually adjusting the transmission ratio may engage theset lever by way of a shaft having an eccentric pin projecting from itsface. The shaft is supported. in the transmission housing. The set levermay be made pivotable about the eccentric pin. The transmission shaftand the pump shaft may be connected by means of a Cardan joint, therebyovercoming the influence of misalignments of the pump shaft relative tothe transmission shaft which may be caused by inaccuracies inproduction.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be more readilycomprehended from the following description when taken in conjunctionwith the appending drawings, wherein:

FIG. 1 is a sectional view of an infinitely variable cone pulleytransmission, comprising one hydraulically controlled side,

FIG. 2 shows the hydraulically controlled side of the transmission on anenlarged scale,

FIG. 3 is a front view of the transmission side shown in FIG. 2 with thehousing which carries the lever for manually adjusting the transmissionratio removed,

FIG. 4 is a sectional view cut along line III-III in FIG. 2.

FIG. 5 is a sectional view cut along line IVIV in FIG. 2,

FIG. 6 shows a second embodiment of the hydraulic control device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings,the transmission shafts 1 and 45 are rotatably mounted in a transmissionhousing 8. The shafts carry one disc pair each, comprising the conediscs 2 and 3 on the driving side of the transmission and 46 and 47 onthe driven side. Between the cone disc pairs is suspended an endlesstransmitting belt 4. The shaft 1 is the driving shaft of thetransmission which is in a suitable manner connected to a driving motor,not shown. The cone disc 47 is displaceable on shaft 46 in the axialdirection but is connected therewith for joint rotation. The cone disc46 is under the influence of a helical coil spring 49 which rests withone end against a flange 48 which is a portion of the shaft 45. Thespring 49 exerts the pressure in axial direction which is needed on thedriven side of the transmission.

The driving side of the transmission illustrated in FIG. 1 is explainedin greater detail with reference to FIG. 2. The cone disc 3 isstationary on the shaft 1, and the cone disc 2 is axially displaceableon but rotatable with the shaft. A flange or piston 5 is a portion ofthe shaft 1 and a cylinder 6 is a portion of the displaceable cone disc2. Piston 5 and cylinder 6 form together a piston-cylinder aggregate bymeans of which the pres sure in axial direction on the transmitting belt4 is generated which is necessary for maintaining or changing thetransmission ratio. In order to keep the transmitting belt from saggingand to provide the necessary tension on the transmitting belt 4 when thetransmission is at rest, when no hydraulically generated pressure iseffective, a helical coil spring 7 is provided which exerts a certaincounter pressure on the cone disc 2 and on the transmitting belt. Thisspring 7 is, of course, also effective when the transmission is not atrest, i.e., when the transmission is in operation, but then itsresilient force is too small to be of any significance.

The conveyance of the hydraulic liquid, for example of hydraulic oil,from the transmission sump 50 which is formed by the housing 8 (FIG. 1)is accomplished by a gear pump. The shaft 9 of the pump is provided witha sealing element and extends into a bore 10 of the transmissionshaft 1. The shaft is mounted in a pump housing 11 and is driven by thetransmission shaft 1 through a claw coupling 12. As will best bediscerned from FIG. 3, the gear pump comprises two gears 13 and 14. Gear13 is carried by the pump shaft 9 while the gear 14 is supported in thepump housing 11. At 15 both gears form together the suction side of thepump. This side is in connection with the oil sump 50 through a suctionline 16 which is formed by holes in the pump housing 11 and in thetransmission housing 8.

The pressure side 17 of the pump is on the one hand connected with thecylinder by way of a recess 18 in a housing portion 19 and through holes20 and 21 which extend in axial direction in the pump shaft 9 and in thetransmission shaft 1 respectively. On the other hand the pressure sideis through the recess 18 connected to a control valve 22 to which thehydraulic oil may pass through the lines 23, 24 and 25. In the controlvalve the oil passes over an edge 26 of a slide member and from there itflows through a hole 27 (FIG. 5) to the rear of a safety valve 27 whichis in connection with a return line 28 formed by a hole in thetransmission housing 8.

Between the axially displaceable cone disc 2 and the control valve 22there is established a mechanical connection by a connection rod 29which extends through the holes 20 and 21. On the one side theconnection rod bears against a bar 30 which traverses a sleeve portionof the cone disc 2 and on the other side it engages a setting lever 31.The latter is linked to the slide member of the control valve 22. Inorder to keep these elements constantly in a backlash-free connection,the slide member of the control valve 22 is under the influence of aspring 32. The setting lever 31 is pivotable about a pin 34 whichprojects eccentrically from the face of a shaft 33. The shaft 33 extendsthrough the wall of the housing 19 and a lever 35 is connected to theshaft outside of the housing. This lever provides a means for manuallyadjusting the position of the set lever 31 by turning the shaft 33.

The already mentioned safety valve 27 is provided in order to protectthe transmission from overload. As shown in FIG. 3 the valve may forexample comprise a ball 38 which is under the resilient force of aspring 37 and which, normally, closes a hole 39 in front of the recess18in the housing 19.

Further, it is of advantage to arrange a throttle valve 40 in the returnflow of the hydraulic oil, in order to ensure in the whole hydrauliccontrol system a minimum pressure, independently from the position whichthe slide member of the control valve 22 may occupy.

On the other side of the transmission, which in the described embodimentis the driven side, the necessary pressure in axial direction on thedisplaceable cone disc 46 is exerted by a helical coil spring 49. Thelatter is so dimensioned that the transmitting belt 4 is at alltransmitted torques safely held between the two cone discs. This means,of course, that the clutch operates constantly under an axial pressurewhich is actually only necessary when the greatest torque is to betransmitted for which the transmission is designed. Since, however, thetransmission is only designed for transmitting relatively small torquesthis may be accepted because it entails a considerable simplicity indesign and, consequently, a noticeable reduction in price.

The hydraulic control device described with reference to the FIGS. 2through 5 operates in the following manner: First let it be assumed thatthe transmission is adjusted to a particular transmission ratio and thatit is balanced in that state. Through the suction line 16 the oil pumptransports oil into the recess 18 and from there through the holes 20and 21 into the pressure chamber 41 of the cylinder/piston aggregate,while the surplus oil flows through the control valve 22 and through thereturn line 28 back into the sump 50. The slide member of the controlvalve 22 is in a position wherein at its edge and also in the pressurechamber 41 a pressure prevails which causes the cone discs 2 and 3 toexert a clamping force on the transmitting belt 4 which conterbalancesthe expanding forces of the belt.

Now, in the event that the cone disc 2 moves to the right (FIG. 2) onaccount of changes in the torque, i.e., if the transmission adjustsitself automatically to a higher number of revolutions on the drivingside, this causes a displacement of the sliding member of the controlvalve to the left by the bar 30, the connection rod 29, and the settinglever 31. Thus the opening in front of the edge 26 increases and moreoil can flow into the return line. As a consequence the pressure in thepressure chamber 41 decreases accordingly. By the expanding force of thetransmitting belt 4 the cone disc is then displaced to the left until,in connection with a corresponding backward movement of the slide memberof the control valve 22 and the increase of the pressure in the pressurechamber 41 caused thereby, a

balance is again established between the clamping force of the conediscs 2 and 3 and the expanding force of the belt 4. A control in thereverse sense takes place when the cone disc 2 moves to the left (FIG.2) as the result of a change of the transmission load, i.e., when thetransmission is going to adjust itself to a lower number of revolutionson the driving side. Since the control valve has a steep characteristicthe hydraulic control device can react very quickly.

In the event that the transmission is to be adjusted manually forexample, to a lower transmission ratio, this can be accomplished by apivoting movement of the lever 35 (FIG. 2) in a counter clockwisedirection. Thereby the pivot of the setting lever 31, which is the pin33, is displaced to the left so that the slide member of the controlvalve 22 is also displaced to the left. Thereby the cross section of thereturn oil flow in front of the edge 26 is enlarged. Now the decrease ofpressure in the pressure chamber 41 causes the cone disc 2 to yield tothe left under the expanding force of the transmitting belt 4 which thenrotates between the cone discs 2 and 3 along a circumference of ashorter radius. This lateral movement of the cone disc 2 comes to astand-still when the displacement of the connection rod 29 in the samedirection as the cone disc 2 and the pivoting movement of the settinglever 31 under the resilient force of the spring 32 has pushed the slidemember of the control valve 22 so far to the right that the increasingpressure in the pressure room 41 again balances the expanding force ofthe belt 4.

FIG. 6 shows an embodiment of the invented hydraulic control device withthe control valve and the safety valve combined in one unit. To this enda conical valve is provided of which the valve cone is on the one handunder the pressure of a spring 32 and on the other hand under theinfluence of a lever 43. The lever 43 is pivotable about the pin 34 andthe valve cone closes more or less an opening 44 in the return line ofthe hydraulic oil. Insofar the conical valve has the function of acontrol valve. If, however, the pressure in the chamber 41 and in therecess 18 rises to a level which corresponds to a torque whichrepresents an overload of the transmission so that the spring on thedriven side of the transmission can no longer exert a force which wouldprevent the belt 4 from slipping, then the conical valve can openautomatically and without any command by the lever 43, provided thespring 32 is chosen properly.

What is claimed is:

1. An infinitely variable cone pulley transmission having a drivingshaft and a driven shaft and a pair of conical discs on each shaft, oneconical disc of each pair being laterally displaceable on the shaft andmechanically connected therewith for joint rotation, and an endlesstransmitting member suspended between the two pairs of conical discs, aspring operatively connected with the displaceable conical disc on oneside of the transmission to urge the disc in the direction of thestationary conical disc, and hydraulic means urging the displaceabledisc on the other side of the transmission in the direction of thestationary eonical disc, said hydraulic means comprising:

a. a gear pump for pumping hydraulic liquid into the transmissionhousing, said gear pump having a housing directly attached to thetransmission housmg;

b. the driving shaft being provided with a bore in its axial directionand a hollow pump shaft extending through said bore into said drivingshaft, and means operatively connecting the pump shaft to the drivingshaft to be driven thereby;

c. means associated with the conical disc and the driving shaft formingtherewith a cylinder-piston aggregate;

d. the axial bore in the driving shaft communicating with the interiorof said piston-cylinder aggregate and said pump shaft being hollow andhaving its interior communicating with the bore in the driving shaft;

e. means for controlling the flow of hydraulic liquid to the cylinderpiston aggregate including a control valve in the pump housing having amovable element;

f. a housing portion adjacent to the pump housing having a spacetherein, a setting lever arranged in said space, one arm of said settinglever being operatively connected with the axially displaceable conicaldisc on the driving shaft, and another arm being operatively connectedto the movable element of the control valve, and manually settable meansoperatively engageable with said lever to adjust the leverage thereof;

g. passages in said transmission housing and said pump housing, forconnecting the pump, the space within the housing portion, the interiorof the hollow pump shaft and the control valve.

2. A transmission as claimed in claim 1, in which said control valveconstitutes a relief valve for permitting the escape of fluid above acertain pressure, and in which said passages include a passage in thetransmission housing communicating with the outlet of said controlvalve.

3. The device as claimed in claim 1, in which a rod extending throughthe interior of the pump shaft and the bore in the driving shaftconstitutes the connection between the axially displaceable conical discand the control lever.

4. A transmission as claimed in claim 1, further comprising a throttlevalve (40) arranged downstream from the control valve.

5. A transmission as claimed in claim 1, wherein the control valve is acontrollable safety valve.

6. A transmission as claimed in claim 1, wherein manually settable meansincludes a lever (35) turnable mounted in the housing portion on whichthe lever is secured, said shaft being provided with an eccentricallyprojecting pin about which the set lever pivots.

7. An infinitely variable cone pulley transmission as claimed in claim1, wherein the transmission shaft and the pump shaft are interconnectedby a Cardan joint.

1. An infinitely variable cone pulley transmission having a drivingshaft and a driven shaft and a pair of conical discs on each shaft, oneconical disc of each pair being laterally displaceable on the shaft andmechanically connected therewith for joint rotation, and an endlesstransmitting member suspended between the two pairs of conical discs, aspring operatively connected with the displaceable conical disc on oneside of the transmission to urge the disc in the direction of thestationary conical disc, and hydraulic means urging the displaceabledisc on the other side of the transmission in the direction of thestationary conical disc, said hydraulic means comprising: a. a gear pumpfor pumping hydraulic liquid into the transmission housing, said gearpump having a housing directly attached to the transmission housing; b.the driving shaft being provided with a bore in its axial direction anda hollow pump shaft extending through said bore into said driving shaft,and means operatively connecting the pump shaft to the driving shaft tobe driven thereby; c. means associated with the conical disc and thedriving shaft forming therewith a cylinder-piston aggregate; d. theaxial bore in the driving shaft communicating with the interior of saidpiston-cylinder aggregate and said pump shaft being hollow and havingits interior communicating with the bore in the driving shaft; e. meansfor controlling the flow of hydraulic liquid to the cylinder pistonaggregate including a control valve in the pump housing having a movableelement; f. a housing portion adjacent to the pump housing having aspace therein, a setting lever arranged in said space, one arm of saidsetting lever being operatively connected with the axially displaceableconical disc on the driving shaft, and another arm being operativelyconnected to the movable element of the control valve, and manuallysettable means operatively engageable with said lever to adjust theleverage thereof; g. passages in said transmission housing and said pumphousing, for connecting the pump, the space within the housing portion,the interior of the hollow pump shaft and the control valve.
 2. Atransmission as claimed in claim 1, in which said control valveconstitutes a relief valve for permitting the escape of fluid above acertain pressure, and in which said passages include a passage in thetransmission housing communicating with the outlet of said controlvalve.
 3. The device as claimed in claim 1, in which a rod extendingthrough the interior of the pump shaft and the bore in the driving shaftconstitutes the connection between the axially displaceable conical discand the control lever.
 4. A transmission as claimed in claim 1, furthercomprising a throttle valve (40) arranged downstream from the controlvalve.
 5. A transmission as claimed in claim 1, wherein the controlvalve is a controllable safety valve.
 6. A transmission as claimed inclaim 1, wherein manually settable means includes a lever (35) turnablemounted in the housing portion on which the lever is secured, said shaftbeing provided with an eccentrically projecting pin about which the setlever pivots.
 7. An infinitely variable cone pulley transmission asclaimed in claim 1, wherein the transmission shaft and the pump shaftare interconnected by a Cardan joint.